But despite his physical fragility, the spirited five-year-old loves nothing more than dressing up as comic book hero Iron Man or ‘Man of Steel’ Superman.

Kaden, from Dallas, Texas, has a brittle bone condition that means his bones can shatter simply by sneezing, but won’t let anything hold him back.

Despite suffering over 40 fractures since birth, he enjoys play fighting, dancing and singing, playing his guitar and racing around on his specially adapted bike – with all the voracity of his beloved Marvel characters.

Kaden’s mum, Valorie Salsman, said: “I think Kaden loves superheroes so much because maybe he partially feels like he is one.

“He’s already overcome so much and achieved what doctors told us would be impossible.

“We were told he wouldn’t survive the birth and that we should plan for a funeral, that he would never breathe on his own, that he would never cry and be in so much pain because of all his fractures.

“From the moment he was laid on my chest I knew he would survive and fulfil his life, and he is so full of life every day.”

Valorie first found out there were problems 20 weeks into her pregnancy.

The 25-year-old said: “They measured his long bones and realized that they were shorter than normal so they referred us to a specialist who got a closer look and they realized that something wasn’t right.

“His bones were very short and he had nine healing fractures on his ribs, arms and legs.”

Kaden was given less than a five per cent chance of survival and doctors recommended a termination, but Valorie and Kaden’s dad, Kelby Casebolt – who are now separated - decided to go against medical advice and proceed with the pregnancy.

Kelby, 26, said: “I didn’t know what to expect but when he was born it was a dream come true. He started crying and we instantly knew he was going to be okay.

“We had a lot to learn over the next weeks and months but we never doubted him and he’s continued to progress and become lively and independent.”

Now Kaden has an active homelife with his mum and stepdad, Benjamin Herzog, who has helped to raise Kaden since he was one year old.

Benjamin said: “When I first met Kaden I didn’t realize how severe the condition was. Shortly after he had his first surgery, and that’s when it hit me that he is going to have to deal with this constantly for the rest of his life and that’s when it got emotional for me.

“But Kaden himself makes it easy. He’s got such a bright personality and the only time he ever shows any type of pain is when he breaks something. He doesn’t let it slow him down ever.”

Despite Kaden’s progression, his bones are still very fragile, and he can even break a bone from a bumpy car ride.

Now he has bilateral rods in his femur and both of his tibias to help stabilize the bowing of his legs from multiple breaks, and to help him walk independently.

To date he has broken over 40 bones, which Valorie has learnt to splint herself, and Kaden continues to astound doctors.

Valorie said: “We actually saw a NICU doctor that treated him a few months ago and she was just amazed about how well he had grown up. At the time he had started to bear weight and walk unassisted and she couldn’t believe it.”

Kaden now attends a regular kindergarten, where his huge personality and character have made him popular with classmates and teachers alike.

Valorie, who is training to become a nurse, said: “Kaden has the biggest personality and I think if I were to describe him in one word it would be ‘fascinating’ because he is so many different things in one.

“He is imaginative, he is creative, he is so kind and he has so much empathy and love for other people. He is everything beautiful – he’s like the sun.”

Despite his young age, Kaden is aware of his condition and the need to be extra-careful.

Valorie said: “Kaden knows when he breaks a bone. He knows when he is injured. He lives fearlessly, but he lives with caution as well. He has had multiple injuries that he has learnt from, caused by falling off the couch or slipping over or standing up too fast. He knows what’s going on by now.

“To think that Kaden knows he isn’t able to do something hurts my heart a little bit, but that’s what he has been given and he plays it well. As long he keeps a positive mind and appositive heart he can do anything.”

Now Valorie, Kelby, and Benjamin, all have high hopes for Kaden’s future.

Benjamin, a construction site manager, said: “I'd really like him to be completely independent - that’s my main hope for him, and I am very confident that he will be.

“My main hope for him is that he would have a long, independent, life.”

Kelby added: “I think what we can learn from Kaden is to be happy, to love life and even though that you have obstacles, tackle them and make the best out of what you have.

"He is such a happy and loving little boy. If he is happy, why can’t anyone else be?”